Piezo electric crystal apparatus



July 7, 1931- A. Mci.. NlcoLsoN 1,813,461

PIEZO ELECTRIC CRYSTAL APPARATUS Filed Dec. 20, 1926 2 Sheets-Sheet l IN V EN TOR.

f ATTORNEY July 7, 1931. A. MCL. NlcoLsoN 1,813,451

PIEZO ELECTRIC CRYSTAL APPARATUS Filed Dec. 20, 1926 2 Sheets-Sheet 2 TCT-: E

duh!- LAmmin f- IN V EN TOR.

' ATTORNEY LSU Patented July 7, 1931 UNITED STATES PATENT OFFICE ALEXANDER MCLEAN NICOLSON, OF N EW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGN- MENTS, TO FEDERAL TELEGRAPH COMPANY, A CORPORATION OF CALIFORNIA t PIEZO ELECTRIC CRYSTAL APPARATUS Application filed December 20, 1926. Serial No. 156,032.

My invention relates broadly to piezo electric crystal apparatus and more particularly to a mounting for piezo electric crystals em-l ployed for the constant frequency control of electrical circuits.

One of the objects of my invention is to provide a crystal holder by which piezo electric crystals may be hermetically sealed against moisture or gases which effect -the proper oscillating characteristics of the piezo electric crystals.

Another object of my invention is to provide a piezo electric crystal mounting for connection in an electrical circuit whereby piezo electric crystals of different frequency characteristics may be readily inserted or removed from the electrical circuit for substituting piezo electric crystals of desired frequency characteristics for the control of electrical circuits at desired frequency.

Still another object of my invention is to provide a holder for piezo electric crystals comprising a housing in which the crystal is positioned and electrically connected to terminals extending exteriorly of the casing protecting the crystal from external foreign matter at the same time that the crystal is free to oscillate in its own natural period without hindrance.

A further obj ect of my invention is to provide amounting for a piezo electric crystal element whereby the element may vibrate at its own natural frequency without restriction for the frequency control of an electrical circuit.

Another' object of my invention is to provide an arrangement of fiexible packing around a piezo electric element within a sealed casing whereby the element may be centered within the casing for free vibration therein without restriction.

My invention will be more fully understood from the specification hereinafter following by referring to the accompanying drawings in which:

Figure 1 is a perspective view illustrating through the piezo electric crystal holder of my invention; Fig. 3 is a lateral cross-sectional view taken through the piezo electric .crystal holder on line 8 3 of Fig 2; Fig. 4 is a top plan view showing the interchangeable mounting of the piezo electric crystal holder of my invention on the support for the crystal holder; Fig. 5 illustrates the interior wiring of the piezo electric crystal apparatus of my invention; and Fig. 6 illustrates the application of the piezo electric crystal apparatus of my invention for the Jfrequency control of radio transmission sysems.

Referring to the drawings in detail reference character 1 designates the piezo electric crystal element which is provided with a pair of conductive coatings or plates 3 and 4 on one side thereof. The opposite face 2 of the piezo electric crystal element 1 rests upon the metallic plate 6 which rforms the bottom closure member for the crystal holder. The crystal holderV consists of an insulated housing 7 having the metallic closure 6 forming one side thereof and being provided with a metallic shield or interior wall 8 forming an enclosure for the piezo electric crystal device 1. Electrostatic shielding of the container is completed by means of an insulated top member 9 having a metallic under-surface 1() which establishes connection with the interior shielding 8 by means of a spring contact 31 so that the piezo electric crystal 1 is clectrostatically shielded within the container. The insulated top member 9 carries binding posts 11, 12 and 13 which connect interioriy of the crystal holder with the several terminals of the piezo electric crystal device. Binding post 11 connects through a conductor 14C with electrode 3 of piezo electric crystal device 1. Binding post 13 connects through lead 15 with electrode 4. The bottom plate 6 which forms part of the electrostatic shielding completed by the walls 8 and conductive top member 10 is electrically connected with walls 8 through spring contact 32. Binding post 12 connects with the shield 8. The binding posts are so positioned on the top of the crystal container that when the container is slipped into position on the mounting 16 with the lower plate 6 thereof resting on the lower surface of the mounting 16 the binding posts establish quick detachable connections, with spring arms extending out from the panel 16. I have represented arms 17 18 and 19 as being forked at their ends to enable connection to be established with the binding posts 11, 12 and 13, respectively. Each of the spring strip members 17, 18 and 19 are provided with a binding post 17a, 18a and 19a, respectively.

, By reasonk of the interchangeable mounting of the crystal holder on the support 16 apiezoelectric crystal device ground to different frequency characteristics may be readily inserted into or removed from the support 16 for the control of an oscillator system of relatively high power.v In order to center the piezo electric crystal element within the casing and yet permit the piezo electric crystal element to vibrate-without restriction I mount aroundV the piezo electric crystal elementl a plurality of blocks of resilient material 20 such as sponge rubber or glass wool. The resilient -material forms ak packing around the lpiezo electric crystal element for centrally locating the piezo electric crystal element within the holder without the exertion of mechanical restraint upon the piezo electric; crystal element. By this arrangement thepiezo electric crystal element 1 is practically supported in free space. molecular movement of the crystal at its loop or zone of maximum dilation is of the order inthe case of ay crystal oscillator of a millionth of an inch and it requires asurface represented by cohesion of metallic density to `produce material damping of a crystal motor'.- InV the present instance the mechanical vibration ofthe crystal element is unrestricted and thepresence yof the blocks of material tal` Y i Y In `Fig. 6 I haveshown the application of the'lpiezo electric crystal apparatus to the fre.

quency control circuit of a transmitter. The oscillator tubes are represented at 21, 22 and 23 arrangedy to function as a whole for the development of high frequency oscillations `undercontrol of thepiezo electric crystal elementl. r The output of the oscillator system is" supplied to the input circuit of the power amplifier system 24 from which the energy isv conveyed to the antennaground system 25 and modulated under control of the circuit TheA electrode 3 of the piezo electric The 20does not impede the movement of the cryscrystal element connects to the grid of electron tube 21 while the lower face 2 connects to the filament circuit. The output electrode 4 connects to the plate electrode of tube 23 while the lower face 2 connects to the other side of the output circuit of the oscillator system. The piezo electric crystal apparatus is so formed that the input circuit of the oscillator connects across the input electrode 3 and the common electrode 2 while the koutput circuit of the oscillator connects across the output electrode t and the common-electrode The arrangement of the piezo electric crystalelement in the control circuit is such as to permit the control of high power signaling energy at high frequency. The metallic casing 8 which is formed around the piezo electric crystal element forms with the top and bottom conductive plates 6 and 10 a complete electrostatic shield for the piezo electric crystal element. The piezo electric crystal element is protected against humidity conditions and changes in temperature by the electrostatic shield of the-container by means of gaskets 27 and 28which are compressed by means of the screws 29 and 30 Vwhich secure the top and bottom sections to the side walls 7. y

Crystals of different frequency characteristics mounted in different containers may be identified by a plate mounted on the exterior of the container givingl the frequency characteristic of the piezo electric crystal element within the container. By selecting the desired piezo electric crystal holder and slipping this holder into the mounting the resilient contacts 17 18 and 19 engage with the terminals 1l, 12 and 13 for establishingquick detachable connection between the circuits of the electron tube oscillator and the piezo electric crystal element'. y

IVhile I have described my invention in a certain preferred embodiment, I desire that it be understood that modifications may be made by those skilled in the artfwithout departing from the spirit of my invention and no limitations .upon my invention are intended other than are imposed by the scope of the appended claims.

lVhat I claim as new and desire'to secure by Letters Patent of the United States is as follows:

l.- Piezo electric crystal apparatus comprising acasing, au electrostatic shield within said casing, a piezo electric crystal element, terminals carried by said casing, a connection between one face of said piezoelectric crystal element andsaid electrostatic shield and a connection between another face of said piezo electric crystal element with the terminals carried by said casing.

2. Piezo elect-ric crystal apparatus comprising a casing, av piezo electric crystall element within said casing, connections with opposite faces of'said piezo electric crystal element and terminals carried by said casing, and a plurality of blocks of resilient material for centrally locating said piezo electric crystal element Within said casing.

3. Piezo electric crystal apparatus oomprising a casing, a piezo electric crystal element positioned within said casing, a plurality of terminals carried by said casing and a packing of soft resilient material positioned around said piezo electric crystal element for centrally locating said element Within said casing in a manner in which said piezo electric crystal element is free to vibrate in its own natural period.

In testimony whereof I affix my signature.

ALEXANDER MCLEAN NICOLSON. 

